De-icing apparatus



Aug. 21, 1956 D. E. BLACKMER ETAL DE-ICING APPARATUS Filed Feb. 9

Unite 2,760,i9i Patented Aug. 21, 1956 ice DE-ICIN G APPARATUS David E. Blackmer, Reading, and John F. Moore, Acton, Mass., assignors, by mesne assignments, to the United States of America as represented by the Secretary at the Navy Application February 15, 1955, Serial No. 488,443

Claims. (Cl. 343704) This invention relates to de-icing apparatus and, more particularly, to de-icing apparatus for an antenna hous- Antennas sheathed in housings transparent to radiation are well known in the art, and are used frequently on aircraft. It is important that such a housing be heated to prevent the formation of ice on the outside wall thereof, since ice absorbs radiation.

The housing cannot be heated directly since the presence of heating elements would adversely aifect radiation from or to the antenna. it is therefore the practice to place the heating element below the radiating surface of the antenna and to rely upon convection currents of the heated air in the interior of the housing to transmit heat to the entire housing. When the height of the antenna housing is large relative to its other dimensions, which is often the case, an excessive amount of heating power is necessary to maintain the top of the antenna housing above the freezing point. This results in the overheat: ing of the section of the antenna housing in proximity to the heater element, which not only wastes heating power, but raises the temperature at the hottest interior spot to a point where solder joints are deleteriously affected.

It is an object of this invention to provide de-icing apparatus which channels the convection currents in the heated air to provide more uniform heating of the surface of the antenna housing.

It is a further object of this invention to provide deicing apparatus which minimizes the heat radiated and conducted directly to the section of the antenna housing in the vicinity of the heating element.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein the sole figure shows a preferred embodiment of an antenna and antenna housing incorporating de-icing apparatus employing the principles of this invention.

Referring now to the figure, waveguide it}, which is attached to base 12, transmits high-frequency energy to and from cylindrical antenna 14. Cylindrical antenna id is sheathed in fiber glass housing 16, which is concern trically disposed with respect to the axis of cylindrical antenna 14.

Planar fiber glass fins 155 and 2t form with cylindrical antenna 14- a partition which extends radially from the ends of the diameter of cylindrical antenna 14 close to the inside wall of housing 16. This partition divides the interior of housing 16 into two portions of substantially equal size.

Curved strip heating element 22, which is supported by socket 24, is concentric with the axis of cylindrical antenna 14 and is contained wholly within one of the portions of housing 16 defined by the partition. Heating current is applied to heating element 22 through receptacle 26.

Surrounding heating element 22 are highly-polished metallic cylindrical thermal shields 28 and 3%, which are coaxial with cylindrical antenna 14 and which are spaced from each other by transite rings 32 and 34.

Heating element 22 heats the air in the interior of housing is. The presence of fins 18 and Ztl and the position of heating element 22 on only one side of fins 1S and creates a convection current which is directed upward on the front side of fins 13 and 2d and downward on the rear side of fins it and 29, as shown by the arrows. The presence of thermal shields 28 and 3t the dead air space which exists between them reduce to a minimum the direct transmission of heat by radiation and conduction from heating element 22 to the section of housing 16 in proximity to heating element 22.

The de-icing apparatus, just described, reduces the power required for heating element 22 and provides more uniform heating of the outside surface of housing 16. For instance, an antenna assembly of the type described herein required only watts of heating power to maintain point 36, the uppermost point of the outer surface of housing 16, above the freezing point. The temperature at the hottest spot in the interior of housing 16 was 104 C., and the temperature of the hottest spot on the outside surface of housing 16 was 12 C. However, when partition fins 15-3 and 2d were omitted and a conventional transite thermal shield was substituted for double-spaced thermal shields 2d and 30, 680 watts were required to maintain point 36 above the freezing point. The temperature of the hottest spot in the interior of housing 16 was, in this case, 320 C. and the hottest spot on the outside surface of housing 16 was 89 C.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. it is therefore to be understood that within the scope of the appended claims the invention be practiced otherwise than as specifically described.

We claim:

1. Apparatus for de-icing an antenna housing having a height which is large relative to its other dimensions, said apparatus comprising a partition located within the interior of said housing and extending substantially parallel to the height of said housing from a small distance above the bottom of said housing to a small distance below the top of said housing for vertically dividing the interior of said housing into two portions of substantially equal size, a heater element located in the vicinity of the bottom of said housing and disposed within only one of said portions, and outer and inner spaced-concentric-metallic-thermal shields located in proximity to the section of the inside wall of said housing adjacent said heater and surrounding said heater element, said thermal shields being substantially parallel to the height of said housing, the height of said thermal shields being small relative to the height of said housing.

2. The apparatus defined in claim 1, wherein said thermal shields have highly polished surfaces and wherein a dead air space exists between said inner and outer thermal shields, whereby the transmission of heat transverse to the surfaces of said thermal shields by radiation and conduction is extremely low.

3. The apparatus defined in claim 1, wherein said housing is concentric about an axis parallel to the height thereof, wherein said partition comprises a cylindrical antenna coaxial with said housing and two planar fins which extend radially from opposite ends of a diameter of said antenna to the inside wall of said housing, wherein said thermal shields are cylinders coaxial with said housing and have diameters slightly smaller than the section of said housing to which they are in proximity, and wherein said heater element is a curved strip coaxial with said housing having an arcuste extent less than 180,

said heater element being located intermediate said inner thermal shield and said antenna wholly on one side of said partition.

4. The apparatus defined in claim 3, wherein said housing and said fins are composed of fiber glass.

5. The apparatus defined in claim 4, wherein said thermal shields have highly polished surfaces and wherein a dead air space exists between said inner and outer thermal shields, whereby the transmission of heat transverse to the surfaces of said thermal shields by radiation and conductien is extremely low.

References Cited in the file of this patent UNITED STATES PATENTS 

